package com.hmdp.service.impl;

import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.RedisConstants;
import com.hmdp.utils.RedisData;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;
import static org.apache.tomcat.jni.Global.trylock;

/**
 * <p>
 * 服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Autowired
    private StringRedisTemplate stringRedisTemplate;

    @Override
    public Result queryById(Long id) {
        //缓存穿透
        //Shop shop =queryWithPassThrough(id);
        // 互斥锁解决缓存击穿
        //Shop shop = queryWithMutex(id);
        //逻辑过期解决缓存击穿
        Shop shop = queryWithLogicalExpire(id);

        if (shop == null) {
            return Result.fail("店铺不存在");
        }
        //返回
        return Result.ok(shop);
    }
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);
    public Shop queryWithLogicalExpire(Long id) {
        String key = "cache:shop:" + id;
        //1.从Redis查询店铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断店铺是否存在
        if (StrUtil.isBlank(shopJson)) {
            //存在，直接返回店铺信息
            return null;
        }
        //命中，需要先把JSON反序列化为对象
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        Shop shop = JSONUtil.toBean((JSONObject) redisData.getData(), Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();
        //判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            //未过期，直接返回店铺信息
            return shop;
        }

        //已过期，需要进行缓存重建
        //缓存重建
        //尝试获取互斥锁
        String lockKey = LOCK_SHOP_KEY+ id;
        boolean isLock = tryLock(lockKey);
        //判断是否获取锁成功
        if (isLock) {
            //成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    this.saveShop2Redis(id, 20L);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    unlock(lockKey);
                }
            });
        }
        //失败，返回过期的商铺信息
        return shop;
        }



    public Shop queryWithMutex(Long id) {
        String key = "cache:shop:" + id;
        //1.从Redis查询店铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断店铺是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            //存在，直接返回店铺信息
            return JSONUtil.toBean(shopJson, Shop.class);
        }
        //3.判断命中的是否是空值
        if (shopJson != null) {
            //4.不存在，返回错误
            return null;
        }
        //不存在，根据id查询数据库
        Shop shop = getById(id);
        //不存在，返回错误
        if (shop == null) {
            //将空值写入Redis
            stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);

            return null;
        }
        //存在，将商铺数据写入Redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop), 30L, TimeUnit.MINUTES);
        //返回
        return shop;
    }

    public <R,ID> R queryWithPassThrough(
            String keyPrefix,ID id, Class<R> typem, Function<ID,R> dbFallback,Long time, TimeUnit unit) {
        String key = keyPrefix+ id;
        //1.从Redis查询店铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断店铺是否存在
        if (StrUtil.isNotBlank(json)) {
            //存在，直接返回店铺信息
            return JSONUtil.toBean(json, type);
        }
        //3.判断命中的是否是空值
        if (json != null) {
            //4.不存在，返回错误
            return null;
        }
            //4.成功，根据id查询数据库
            R r = dbFallback.apply(id);
            //不存在，返回错误
            if (r == null) {
                //将空值写入Redis
                stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);

                return null;
            }
            //存在，将商铺数据写入Redis
            stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(r), 30L, TimeUnit.MINUTES);

            return shop;
        }


    }

    @Override
    @Transactional()
    public Result update(Shop shop) {
        Long id = shop.getId();
        if (id == null) {
            return Result.fail("店铺id不能为空");
        }
        //更新数据库
        updateById(shop);
        //删除缓存
        stringRedisTemplate.delete(RedisConstants.CACHE_SHOP_KEY + id);
        return Result.ok();
    }


    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return Boolean.TRUE.equals(flag);
    }

    private void unlock(String key) {
        stringRedisTemplate.delete(key);
    }

    public void saveShop2Redis(Long id, Long expireSeconds) throws InterruptedException {
        //1.查询店铺数据
        Shop shop = getById(id);
        Thread.sleep(200);
        //2.封装逻辑过期时间
        RedisData redisData = new RedisData();
        //3.写入Redis
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));
        //4.设置过期时间
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(redisData));

    }

}
